The continuing goal of the work proposed for the competitive renewal is to generate and identify AIDS vaccine components from combinatorial libraries of chimeric human rhinoviruses (HRVs) displaying HIV-1 immunogens. We use the technique of random systematic mutagenesis to generate libraries of chimeric HRVs that display HIV-1 epitopes with many varying lengths, sequences, and conformations. We then use immunoselection to enrich for chimeras with desired features of antigenicity. The first four years of this grant allowed us to demonstrate the success with which this system has led to chimeras that effectively display HIV-1 epitopes. Four libraries were generated and characterized, two displaying V3 loop sequences from gp120 and two displaying the conserved ELDKWA epitope from gp41. This work led to the identification of three V3 loop chimeras that elicited anti-HIV-1 neutralizing responses among the most potent reported for any AIDS vaccine system. The ELDKWA chimeras as well as some V3 loop chimeras displaying composite sequences are now being characterized for their ability to neutralize diverse isolates of HIV-1. The preliminary data indicate that a number of primary isolates can be neutralized by antisera against these chimeras. In another experiment, four chronically HIV-infected chimpanzees were immunized with either of two V3 loop chimeras, resulting in boosted V3 loop-specific immune responses. In this renewal application, two HRV14:HIV-1 composite-sequence V3 loop libraries will be constructed and/or characterized. One involves "cross-clade" V3 loop sequences and the other involves clade B sequences. In addition, two libraries will be constructed and characterized that will display the ELDKWA immunogen (using different linkers and insertion sites). Immunoselected chimeras that are neutralized well by diverse anti-HIV-1 antibodies will be used to immunize guinea pigs. Antisera elicited by HRV14:HIV-1 chimeras will be assayed for their ability to neutralize both laboratory-adapted and primary isolates of HIV-1. We will also explore the potential for immunizing rhesus macaques with HRVs displaying the SIV Mamu-A*01 MHC class I restricted gag CTL epitope, CTPYDINQM. We will work with Dr. David Watkins of the Wisconsin Regional Primate Research Center to see if HRV can replicate in macaque cells. If so, one or two macaques will be immunized with HRV14. If HRV14 replicates, we will pursue immunization of Mamu-A*01 macaques with chimeric viruses and monitor the SIV-directed CTL responses. The chimeric HRV:HIV system complements the many other vaccine systems being explored in an effort to develop an AIDS vaccine. HRV:HIV chimeras have the potential to serve as live-virus vaccine components, capable of stimulating humoral, mucosal and, perhaps, cell-mediated immune responses.